Method and device for transmitting data unit

ABSTRACT

A transmitting device of the present invention submits, from a packet data convergence protocol (PDCP) entity configured with a PDCP duplication function, a PDCP protocol data unit (PDU) (duplicated PDCP PDU 1) to a lower layer and starts a prohibit timer for the duplicated PDCP PDU 1. The transmitting device submits, from the PDCP entity, the same PDCP PDU (duplicated PDCP PDU 2) to the lower layer if the prohibit timer expires. The transmitting device transmit the duplicated PDCP PDU 1 and the duplicated PDCP PDU 2.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT International ApplicationNo. PCT/KR2018/005177, filed on May 4, 2018, which claims the benefit ofU.S. Provisional Application No. 62/501,691, filed on May 4, 2017, whichare all hereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for transmitting a data unit and anapparatus therefor.

BACKGROUND ART

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARD)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

As more and more communication devices demand larger communicationcapacity, there is a need for improved mobile broadband communicationcompared to existing RAT. Also, massive machine type communication(MTC), which provides various services by connecting many devices andobjects, is one of the major issues to be considered in the nextgeneration communication. In addition, a communication system designconsidering a service/UE sensitive to reliability and latency is beingdiscussed. The introduction of next-generation RAT, which takes intoaccount such advanced mobile broadband communication, massive MTC(mMCT), and ultra-reliable and low latency communication (URLLC), isbeing discussed.

DISCLOSURE Technical Problem

Due to introduction of new radio communication technology, the number ofuser equipments (UEs) to which a BS should provide a service in aprescribed resource region increases and the amount of data and controlinformation that the BS should transmit to the UEs increases. Since theamount of resources available to the BS for communication with the UE(s)is limited, a new method in which the BS efficiently receives/transmitsuplink/downlink data and/or uplink/downlink control information usingthe limited radio resources is needed.

With development of technologies, overcoming delay or latency has becomean important challenge. Applications whose performance criticallydepends on delay/latency are increasing. Accordingly, a method to reducedelay/latency compared to the legacy system is demanded.

Also, a method for transmitting/receiving signals effectively in asystem supporting new radio access technology is required.

The technical objects that can be achieved through the present inventionare not limited to what has been particularly described hereinabove andother technical objects not described herein will be more clearlyunderstood by persons skilled in the art from the following detaileddescription.

Technical Solution

In an aspect of the present invention, provided herein is a method fortransmitting a data unit by a transmitting device in a wirelesscommunication system. The method comprises: submitting, by a packet dataconvergence protocol (PDCP) entity configured with a PDCP duplicationfunction, a PDCP protocol data unit (PDU) (duplicated PDCP PDU 1) to alower layer and starting a prohibit timer for the duplicated PDCP PDU 1;submitting, by the PDCP entity, the same PDCP PDU (duplicated PDCP PDU2) to the lower layer if the prohibit timer expires; and transmittingthe duplicated PDCP PDU 1 and the duplicated PDCP PDU 2.

In another aspect of the present invention, provided herein is atransmitting device for transmitting a data unit in a wirelesscommunication system. The transmitting device is equipped with atransceiver and a processor configured to control the transceiver. Theprocessor is configured to: submit, by a packet data convergenceprotocol (PDCP) entity configured with a PDCP duplication function, aPDCP protocol data unit (PDU) (duplicated PDCP PDU 1) to a lower layerand start a prohibit timer for the duplicated PDCP PDU 1; submit, by thePDCP entity, the same PDCP PDU (duplicated PDCP PDU 2) to the lowerlayer if the prohibit timer expires; and control the transceiver totransmit the duplicated PDCP PDU 1 and the duplicated PDCP PDU 2.

In each aspect of the present invention, the PDCP entity may not submitthe duplicated PDCP PDU 2 to the lower layer while the prohibit timer isrunning.

In each aspect of the present invention, the prohibit timer may becounted in units of time period or in units of PDCP PDUs submitted tothe lower layer.

In each aspect of the present invention, the prohibit timer may run perduplicated PDCP PDU.

In each aspect of the present invention, the PDCP entity may start theprohibit timer for the duplicated PDCP PDU 2 when submitting theduplicated PDCP PDU 2 to the lower layer, if the duplicated PDCP PDU 2is not the last duplication of the PDCP PDU.

In each aspect of the present invention, the PDCP entity may beconfigured with a number of PDCP PDU duplicates, that the PDCP entity isto generate per PDCP PDU, by a network.

In each aspect of the present invention, the PDCP entity may beconfigured with the PDCP duplication function by a network. The PDCPentity may be configured with the prohibit timer by the network.

In each aspect of the present invention, the transmitting device may bea user equipment.

The above technical solutions are merely some parts of the embodimentsof the present invention and various embodiments into which thetechnical features of the present invention are incorporated can bederived and understood by persons skilled in the art from the followingdetailed description of the present invention.

Advantageous Effects

According to the present invention, radio communication signals can beefficiently transmitted/received. Therefore, overall throughput of aradio communication system can be improved.

According to an embodiment of the present invention, delay/latencyoccurring during communication between a user equipment and a BS may bereduced.

Also, signals in a new radio access technology system can betransmitted/received effectively.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved through the present invention are not limited towhat has been particularly described hereinabove and other advantages ofthe present invention will be more clearly understood from the followingdetailed description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system.

FIG. 2 is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS).

FIG. 3 is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

FIG. 4 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard.

FIG. 5 is a view showing an example of a physical channel structure usedin an E-UMTS system.

FIG. 6 illustrates a data flow example at a transmitting device in theNR system.

FIG. 7 illustrates an example of a PDCP duplication according to thepresent invention.

FIG. 8 is a block diagram illustrating elements of a transmitting device100 and a receiving device 200 for implementing the present invention.

MODE FOR INVENTION

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the invention. Thefollowing detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details.

In some instances, known structures and devices are omitted or are shownin block diagram form, focusing on important features of the structuresand devices, so as not to obscure the concept of the present invention.The same reference numbers will be used throughout this specification torefer to the same or like parts.

The following techniques, apparatuses, and systems may be applied to avariety of wireless multiple access systems. Examples of the multipleaccess systems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency division multipleaccess (SC-FDMA) system, and a multicarrier frequency division multipleaccess (MC-FDMA) system. CDMA may be embodied through radio technologysuch as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe embodied through radio technology such as global system for mobilecommunications (GSM), general packet radio service (GPRS), or enhanceddata rates for GSM evolution (EDGE). OFDMA may be embodied through radiotechnology such as institute of electrical and electronics engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA(E-UTRA). UTRA is a part of a universal mobile telecommunications system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employsOFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolvedversion of 3GPP LTE. For convenience of description, it is assumed thatthe present invention is applied to 3GPP based wireless communicationsystem. However, the technical features of the present invention are notlimited thereto. For example, although the following detaileddescription is given based on a mobile communication systemcorresponding to a 3GPP based system, aspects of the present inventionthat are not limited to 3GPP based system are applicable to other mobilecommunication systems.

For example, the present invention is applicable to contention basedcommunication such as Wi-Fi as well as non-contention basedcommunication as in the 3GPP based system in which an eNB allocates aDL/UL time/frequency resource to a UE and the UE receives a DL signaland transmits a UL signal according to resource allocation of the eNB.In a non-contention based communication scheme, an access point (AP) ora control node for controlling the AP allocates a resource forcommunication between the UE and the AP, whereas, in a contention basedcommunication scheme, a communication resource is occupied throughcontention between UEs which desire to access the AP. The contentionbased communication scheme will now be described in brief. One type ofthe contention based communication scheme is carrier sense multipleaccess (CSMA). CSMA refers to a probabilistic media access control (MAC)protocol for confirming, before a node or a communication devicetransmits traffic on a shared transmission medium (also called a sharedchannel) such as a frequency band, that there is no other traffic on thesame shared transmission medium. In CSMA, a transmitting devicedetermines whether another transmission is being performed beforeattempting to transmit traffic to a receiving device. In other words,the transmitting device attempts to detect presence of a carrier fromanother transmitting device before attempting to perform transmission.Upon sensing the carrier, the transmitting device waits for anothertransmission device which is performing transmission to finishtransmission, before performing transmission thereof. Consequently, CSMAcan be a communication scheme based on the principle of “sense beforetransmit” or “listen before talk”. A scheme for avoiding collisionbetween transmitting devices in the contention based communicationsystem using CSMA includes carrier sense multiple access with collisiondetection (CSMA/CD) and/or carrier sense multiple access with collisionavoidance (CSMA/CA). CSMA/CD is a collision detection scheme in a wiredlocal area network (LAN) environment. In CSMA/CD, a personal computer(PC) or a server which desires to perform communication in an Ethernetenvironment first confirms whether communication occurs on a networkand, if another device carries data on the network, the PC or the serverwaits and then transmits data. That is, when two or more users (e.g.PCs, UEs, etc.) simultaneously transmit data, collision occurs betweensimultaneous transmission and CSMA/CD is a scheme for flexiblytransmitting data by monitoring collision. A transmitting device usingCSMA/CD adjusts data transmission thereof by sensing data transmissionperformed by another device using a specific rule. CSMA/CA is a MACprotocol specified in IEEE 802.11 standards. A wireless LAN (WLAN)system conforming to IEEE 802.11 standards does not use CSMA/CD whichhas been used in IEEE 802.3 standards and uses CA, i.e. a collisionavoidance scheme. Transmission devices always sense carrier of a networkand, if the network is empty, the transmission devices wait fordetermined time according to locations thereof registered in a list andthen transmit data. Various methods are used to determine priority ofthe transmission devices in the list and to reconfigure priority. In asystem according to some versions of IEEE 802.11 standards, collisionmay occur and, in this case, a collision sensing procedure is performed.A transmission device using CSMA/CA avoids collision between datatransmission thereof and data transmission of another transmissiondevice using a specific rule.

In the present invention, the term “assume” may mean that a subject totransmit a channel transmits the channel in accordance with thecorresponding “assumption”. This may also mean that a subject to receivethe channel receives or decodes the channel in a form conforming to the“assumption”, on the assumption that the channel has been transmittedaccording to the “assumption”.

In the present invention, a user equipment (UE) may be a fixed or mobiledevice. Examples of the UE include various devices that transmit andreceive user data and/or various kinds of control information to andfrom a base station (BS). The UE may be referred to as a terminalequipment (TE), a mobile station (MS), a mobile terminal (MT), a userterminal (UT), a subscriber station (SS), a wireless device, a personaldigital assistant (PDA), a wireless modem, a handheld device, etc. Inaddition, in the present invention, a BS generally refers to a fixedstation that performs communication with a UE and/or another B S, andexchanges various kinds of data and control information with the UE andanother BS. The BS may be referred to as an advanced base station (ABS),a node-B (NB), an evolved node-B (eNB), a base transceiver system (BTS),an access point (AP), a processing server (PS), etc. Especially, a BS ofthe UMTS is referred to as a NB, a BS of the EPC/LTE is referred to asan eNB, and a BS of the new radio (NR) system is referred to as a gNB.

In the present invention, a node refers to a fixed point capable oftransmitting/receiving a radio signal through communication with a UE.Various types of eNBs may be used as nodes irrespective of the termsthereof. For example, a BS, a node B (NB), an e-node B (eNB), apico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, etc. maybe a node. In addition, the node may not be an eNB. For example, thenode may be a radio remote head (RRH) or a radio remote unit (RRU). TheRRH or RRU generally has a lower power level than a power level of aneNB. Since the RRH or RRU (hereinafter, RRH/RRU) is generally connectedto the eNB through a dedicated line such as an optical cable,cooperative communication between RRH/RRU and the eNB can be smoothlyperformed in comparison with cooperative communication between eNBsconnected by a radio line. At least one antenna is installed per node.The antenna may mean a physical antenna or mean an antenna port or avirtual antenna.

In the present invention, a cell refers to a prescribed geographicalarea to which one or more nodes provide a communication service.Accordingly, in the present invention, communicating with a specificcell may mean communicating with an eNB or a node which provides acommunication service to the specific cell. In addition, a DL/UL signalof a specific cell refers to a DL/UL signal from/to an eNB or a nodewhich provides a communication service to the specific cell. A nodeproviding UL/DL communication services to a UE is called a serving nodeand a cell to which UL/DL communication services are provided by theserving node is especially called a serving cell.

Meanwhile, a 3GPP based system uses the concept of a cell in order tomanage radio resources and a cell associated with the radio resources isdistinguished from a cell of a geographic region.

A “cell” of a geographic region may be understood as coverage withinwhich a node can provide service using a carrier and a “cell” of a radioresource is associated with bandwidth (BW) which is a frequency rangeconfigured by the carrier. Since DL coverage, which is a range withinwhich the node is capable of transmitting a valid signal, and ULcoverage, which is a range within which the node is capable of receivingthe valid signal from the UE, depends upon a carrier carrying thesignal, the coverage of the node may be associated with coverage of the“cell” of a radio resource used by the node. Accordingly, the term“cell” may be used to indicate service coverage of the node sometimes, aradio resource at other times, or a range that a signal using a radioresource can reach with valid strength at other times.

Meanwhile, the recent 3GPP based wireless communication standard usesthe concept of a cell to manage radio resources. The “cell” associatedwith the radio resources is defined by combination of downlink resourcesand uplink resources, that is, combination of DL component carrier (CC)and UL CC. The cell may be configured by downlink resources only, or maybe configured by downlink resources and uplink resources. If carrieraggregation is supported, linkage between a carrier frequency of thedownlink resources (or DL CC) and a carrier frequency of the uplinkresources (or UL CC) may be indicated by system information. Forexample, combination of the DL resources and the UL resources may beindicated by linkage of system information block type 2 (SIM). In thiscase, the carrier frequency means a center frequency of each cell or CC.A cell operating on a primary frequency may be referred to as a primarycell (Pcell) or PCC, and a cell operating on a secondary frequency maybe referred to as a secondary cell (Scell) or SCC. The carriercorresponding to the Pcell on downlink will be referred to as a downlinkprimary CC (DL PCC), and the carrier corresponding to the Pcell onuplink will be referred to as an uplink primary CC (UL PCC). A Scellmeans a cell that may be configured after completion of radio resourcecontrol (RRC) connection establishment and used to provide additionalradio resources. The Scell may form a set of serving cells for the UEtogether with the Pcell in accordance with capabilities of the UE. Thecarrier corresponding to the Scell on the downlink will be referred toas downlink secondary CC (DL SCC), and the carrier corresponding to theScell on the uplink will be referred to as uplink secondary CC (UL SCC).Although the UE is in RRC-CONNECTED state, if it is not configured bycarrier aggregation or does not support carrier aggregation, a singleserving cell configured by the Pcell only exists.

In the present invention, “PDCCH” refers to a PDCCH, an EPDCCH (insubframes when configured), a MTC PDCCH (MPDCCH), for an RN with R-PDCCHconfigured and not suspended, to the R-PDCCH or, for NB-IoT to thenarrowband PDCCH (NPDCCH).

In the present invention, monitoring a channel implies attempting todecode the channel. For example, monitoring a PDCCH implies attemptingto decode PDCCH(s) (or PDCCH candidates).

In the present invention, for dual connectivity operation the term“special Cell” refers to the PCell of the master cell group (MCG) or thePSCell of the secondary cell group (SCG), otherwise the term SpecialCell refers to the PCell. The MCG is a group of serving cells associatedwith a master eNB (MeNB) which terminates at least S1-MME, and the SCGis a group of serving cells associated with a secondary eNB (SeNB) thatis providing additional radio resources for the UE but is not the MeNB.The SCG is comprised of a primary SCell (PSCell) and optionally one ormore SCells. In dual connectivity, two MAC entities are configured inthe UE: one for the MCG and one for the SCG. Each MAC entity isconfigured by RRC with a serving cell supporting PUCCH transmission andcontention based Random Access. In this specification, the term SpCellrefers to such cell, whereas the term SCell refers to other servingcells. The term SpCell either refers to the PCell of the MCG or thePSCell of the SCG depending on if the MAC entity is associated to theMCG or the SCG, respectively.

In the present invention, “C-RNTI” refers to a cell RNTI, “SI-RNTI”refers to a system information RNTI, “P-RNTI” refers to a paging RNTI,“RA-RNTI” refers to a random access RNTI, “SC-RNTI” refers to a singlecell RNTI″, “SL-RNTI” refers to a sidelink RNTI, and “SPS C-RNTI” refersto a semi-persistent scheduling C-RNTI.

For terms and technologies which are not specifically described amongthe terms of and technologies employed in this specification, 3GPPLTE/LTE-A standard documents, for example, 3GPP TS 36.211, 3GPP TS36.212, 3GPP TS 36.213, 3GPP TS 36.300, 3GPP TS 36.321, 3GPP TS 36.322,3GPP TS 36.323 and 3GPP TS 36.331, and 3GPP NR standard documents, forexample, 3GPP TS 38.211, 3GPP TS 38.213, 3GPP TS 38.214, 3GPP TS 38.300,3GPP TS 38.321, 3GPP TS 38.322, 3GPP TS 38.323 and 3GPP TS 38.331 may bereferenced.

FIG. 2 is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNB 20 to UE 10,and “uplink” refers to communication from the UE to an eNB.

FIG. 3 is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 3, an eNB 20 provides end points of a user planeand a control plane to the UE 10. MME/SAE gateway 30 provides an endpoint of a session and mobility management function for UE 10. The eNBand MME/SAE gateway may be connected via an S1 interface.

The eNB 20 is generally a fixed station that communicates with a UE 10,and may also be referred to as a base station (BS) or an access point.One eNB 20 may be deployed per cell. An interface for transmitting usertraffic or control traffic may be used between eNBs 20.

The MME provides various functions including NAS signaling to eNBs 20,NAS signaling security, AS Security control, Inter CN node signaling formobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, roaming,authentication, bearer management functions including dedicated bearerestablishment, support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNB 20 and gateway 30 viathe S1 interface. The eNBs 20 may be connected to each other via an X2interface and neighboring eNBs may have a meshed network structure thathas the X2 interface.

As illustrated, eNB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 4 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

Layer 1 (i.e. L1) of the 3GPP LTE/LTE-A system is corresponding to aphysical layer. A physical (PHY) layer of a first layer (Layer 1 or L1)provides an information transfer service to a higher layer using aphysical channel. The PHY layer is connected to a medium access control(MAC) layer located on the higher layer via a transport channel. Data istransported between the MAC layer and the PHY layer via the transportchannel. Data is transported between a physical layer of a transmittingside and a physical layer of a receiving side via physical channels. Thephysical channels use time and frequency as radio resources. In detail,the physical channel is modulated using an orthogonal frequency divisionmultiple access (OFDMA) scheme in downlink and is modulated using asingle carrier frequency division multiple access (SC-FDMA) scheme inuplink.

Layer 2 (i.e. L2) of the 3GPP LTE/LTE-A system is split into thefollowing sublayers: Medium Access Control (MAC), Radio Link Control(RLC) and Packet Data Convergence Protocol (PDCP). The MAC layer of asecond layer (Layer 2 or L2) provides a service to a radio link control(RLC) layer of a higher layer via a logical channel. The RLC layer ofthe second layer supports reliable data transmission. A function of theRLC layer may be implemented by a functional block of the MAC layer. Apacket data convergence protocol (PDCP) layer of the second layerperforms a header compression function to reduce unnecessary controlinformation for efficient transmission of an Internet protocol (IP)packet such as an IP version 4 (IPv4) packet or an IP version 6 (IPv6)packet in a radio interface having a relatively small bandwidth.

The main services and functions of the MAC sublayer include: mappingbetween logical channels and transport channels;multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels; scheduling information reporting;error correction through HARQ; priority handling between logicalchannels of one UE; priority handling between UEs by means of dynamicscheduling; MBMS service identification; transport format selection; andpadding.

The main services and functions of the RLC sublayer include: transfer ofupper layer protocol data units (PDUs); error correction through ARQ(only for acknowledged mode (AM) data transfer); concatenation,segmentation and reassembly of RLC service data units (SDUs) (only forunacknowledged mode (UM) and acknowledged mode (AM) data transfer);re-segmentation of RLC data PDUs (only for AM data transfer); reorderingof RLC data PDUs (only for UM and AM data transfer); duplicate detection(only for UM and AM data transfer); protocol error detection (only forAM data transfer); RLC SDU discard (only for UM and AM data transfer);and RLC re-establishment, except for a NB-IoT UE that only uses ControlPlane CIoT EPS optimizations. Radio Bearers are not characterized by afixed sized data unit (e.g. a fixed sized RLC PDU).

The main services and functions of the PDCP sublayer for the user planeinclude: header compression and decompression: ROHC only; transfer ofuser data; in-sequence delivery of upper layer PDUs at PDCPre-establishment procedure for RLC AM; for split bearers in DC and LWAbearers (only support for RLC AM): PDCP PDU routing for transmission andPDCP PDU reordering for reception; duplicate detection of lower layerSDUs at PDCP re-establishment procedure for RLC AM; retransmission ofPDCP SDUs at handover and, for split bearers in DC and LWA bearers, ofPDCP PDUs at PDCP data-recovery procedure, for RLC AM; ciphering anddeciphering; timer-based SDU discard in uplink. The main services andfunctions of the PDCP for the control plane include: ciphering andintegrity protection; and transfer of control plane data. For split andLWA bearers, PDCP supports routing and reordering. For DRBs mapped onRLC AM and for LWA bearers, the PDCP entity uses the reordering functionwhen the PDCP entity is associated with two AM RLC entities, when thePDCP entity is configured for a LWA bearer; or when the PDCP entity isassociated with one AM RLC entity after it was, according to the mostrecent reconfiguration, associated with two AM RLC entities orconfigured for a LWA bearer without performing PDCP re-establishment.

Layer 3 (i.e. L3) of the LTE/LTE-A system includes the followingsublayers: Radio Resource Control (RRC) and Non Access Stratum (NAS). Aradio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other. The non-access stratum (NAS) layer positioned over the RRClayer performs functions such as session management and mobilitymanagement.

Radio bearers are roughly classified into (user) data radio bearers (DRBs) and signaling radio bearers (SRBs). SRBs are defined as radio bearers(RBs) that are used only for the transmission of RRC and NAS messages.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 5 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. The PDCCH carries schedulingassignments and other control information. In FIG. 5, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information.

A time interval in which one subframe is transmitted is defined as atransmission time interval (TTI). Time resources may be distinguished bya radio frame number (or radio frame index), a subframe number (orsubframe index), a slot number (or slot index), and the like. TTI refersto an interval during which data may be scheduled. For example, in the3GPP LTE/LTE-A system, an opportunity of transmission of an UL grant ora DL grant is present every 1 ms, and the UL/DL grant opportunity doesnot exists several times in less than 1 ms. Therefore, the TTI in thelegacy 3GPP LTE/LTE-A system is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation. In the present invention, a PDCCH addressed to a certainRNTI means that the PDCCH is CRC-masked with the certain RNTI. A UE mayattempt to decode a PDCCH using the certain RNTI if the UE is monitoringa PDCCH addressed to the certain RNTI.

A fully mobile and connected society is expected in the near future,which will be characterized by a tremendous amount of growth inconnectivity, traffic volume and a much broader range of usagescenarios. Some typical trends include explosive growth of data traffic,great increase of connected devices and continuous emergence of newservices. Besides the market requirements, the mobile communicationsociety itself also requires a sustainable development of theeco-system, which produces the needs to further improve systemefficiencies, such as spectrum efficiency, energy efficiency,operational efficiency and cost efficiency. To meet the aboveever-increasing requirements from market and mobile communicationsociety, next generation access technologies are expected to emerge inthe near future.

Building upon its success of IMT-2000 (3G) and IMT-Advanced (4G), 3GPPhas been devoting its effort to IMT-2020 (5G) development sinceSeptember 2015. 5G New Radio (NR) is expected to expand and supportdiverse use case scenarios and applications that will continue beyondthe current IMT-Advanced standard, for instance, enhanced MobileBroadband (eMBB), Ultra Reliable Low Latency Communication (URLLC) andmassive Machine Type Communication (mMTC). eMBB is targeting high datarate mobile broadband services, such as seamless data access bothindoors and outdoors, and AR/VR applications; URLLC is defined forapplications that have stringent latency and reliability requirements,such as vehicular communications that can enable autonomous driving andcontrol network in industrial plants; mMTC is the basis for connectivityin IoT, which allows for infrastructure management, environmentalmonitoring, and healthcare applications.

The overall protocol stack architecture for the NR system might besimilar to that of the LTE/LTE-A system, but some functionalities of theprotocol stacks of the LTE/LTE-A system should be modified in the NRsystem in order to resolve the weakness or drawback of LTE. RAN WG2 forNR is in charge of the radio interface architecture and protocols. Thenew functionalities of the control plane include the following:on-demand system information delivery to reduce energy consumption andmitigate interference, two-level (i.e. Radio Resource Control (RRC) andMedium Access Control (MAC)) mobility to implement seamless handover,beam based mobility management to accommodate high frequency, RRCinactive state to reduce state transition latency and improve UE batterylife. The new functionalities of the user plane aim at latency reductionby optimizing existing functionalities, such as concatenation andreordering relocation, and RLC out of order delivery. In addition, a newuser plane AS protocol layer named as Service Data Adaptation Protocol(SDAP) has been introduced to handle flow-based Quality of Service (QoS)framework in RAN, such as mapping between QoS flow and a data radiobearer, and QoS flow ID marking. Hereinafter the layer 2 according tothe current agreements for NR is briefly discussed.

The layer 2 of NR is split into the following sublayers: Medium AccessControl (MAC), Radio Link Control (RLC), Packet Data ConvergenceProtocol (PDCP) and Service Data Adaptation Protocol (SDAP). Thephysical layer offers to the MAC sublayer transport channels, the MACsublayer offers to the RLC sublayer logical channels, the RLC sublayeroffers to the PDCP sublayer RLC channels, the PDCP sublayer offers tothe SDAP sublayer radio bearers, and the SDAP sublayer offers to 5GC QoSflows. Radio bearers are categorized into two groups: data radio bearers(DRB) for user plane data and signalling radio bearers (SRB) for controlplane data.

The main services and functions of the MAC sublayer of NR include:mapping between logical channels and transport channels;multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels; scheduling information reporting;error correction through HARQ (one HARQ entity per carrier in case ofcarrier aggregation); priority handling between UEs by means of dynamicscheduling; priority handling between logical channels of one UE bymeans of logical channel prioritization; and padding. A single MACentity can support one or multiple numerologies and/or transmissiontimings and mapping restrictions in logical channel prioritisationcontrols which numerology and/or transmission timing a logical channelcan use.

The RLC sublayer of NR supports three transmission modes: TransparentMode (TM); Unacknowledged Mode (UM); Acknowledged Mode (AM). The RLCconfiguration is per logical channel with no dependency on numerologiesand/or TTI durations, and ARQ can operate on any of the numerologiesand/or TTI durations the logical channel is configured with. For SRB0,paging and broadcast system information, TM mode is used. For other SRBsAM mode used. For DRBs, either UM or AM mode are used. The main servicesand functions of the RLC sublayer depend on the transmission mode andinclude: transfer of upper layer PDUs; sequence numbering independent ofthe one in PDCP (UM and AM); error correction through ARQ (AM only);segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs;Reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDUdiscard (AM and UM); RLC re-establishment; and protocol error detection(AM only). The ARQ within the RLC sublayer of NR has the followingcharacteristics: ARQ retransmits RLC PDUs or RLC PDU segments based onRLC status reports; polling for RLC status report is used when needed byRLC; and RLC receiver can also trigger RLC status report after detectinga missing RLC PDU or RLC PDU segment.

The main services and functions of the PDCP sublayer of NR for the userplane include: sequence numbering; header compression and decompression:ROHC only; transfer of user data; reordering and duplicate detection;PDCP PDU routing (in case of split bearers); retransmission of PDCPSDUs; ciphering, deciphering and integrity protection; PDCP SDU discard;PDCP re-establishment and data recovery for RLC AM; and duplication ofPDCP PDUs. The main services and functions of the PDCP sublayer of NRfor the control plane include: sequence numbering; ciphering,deciphering and integrity protection; transfer of control plane data;reordering and duplicate detection; and duplication of PDCP PDUs.

The main services and functions of SDAP include: mapping between a QoSflow and a data radio bearer; marking QoS flow ID (QFI) in both DL andUL packets. A single protocol entity of SDAP is configured for eachindividual PDU session. Compared to LTE's QoS framework, which isbearer-based, the 5G system adopts the QoS flow-based framework. The QoSflow-based framework enables flexible mapping of QoS flow to DRB bydecoupling QoS flow and the radio bearer, allowing more flexible QoScharacteristic configuration.

FIG. 6 illustrates a data flow example at a transmitting device in theNR system.

In FIG. 6, an RB denotes a radio bearer. Referring to FIG. 6, atransport block is generated by MAC by concatenating two RLC PDUs fromRB_(x) and one RLC PDU from RB_(y). The two RLC PDUs from RB_(x) eachcorresponds to one IP packet (n and n+1) while the RLC PDU from RB_(y)is a segment of an IP packet (m).

In URLLC, packets must be correctly received with ultra-highreliability, which can be 99.999%, within the required latency target.Since the latency target may be as low as 1 ms, existing techniques,such as HARQ, may not be sufficient for ultra-high reliability. Packetduplication can be used to increase the reliability for both the userdata and control signaling within the required latency target and can beused instead of link selection. The same techniques can also improvemobility robustness including in challenging scenarios such as highmobility and ultra-dense deployments. During the 3GPP meetings for theNR system, there were discussions on the use of dual connectivity (DC)and multi-connectivity (MC) architectures with packet duplication acrossmultiple links to ensure high reliability such as required to supportURLLC. During the 3GPP meetings for the NR system, it was agreed thatpacket duplication is supported for user plane and control plane in PDCPof NR (i.e. NR-PDCP) and that the PDCP function in the transmittersupports packet duplication and the PDCP function in the receiversupports duplicate packet removal. To this end, in NR, a PDCP at atransmitter needs to be modified to introduce a duplication function. Inother words, in NR, the PDCP at the transmitter should be able toduplicate a PDCP PDU and transmit them to multiple RLC entities (orLTE-WLAN Aggregation Adaptation Protocol (LWAAP) entities for LTE-WLANAggregation (LWA) case).

It is not yet decided whether to support PDCP duplicates on the samecarrier with some restriction to prevent them from being transmitted onthe same transport block. As PDCP duplication may not be visible inlower layers, PDCP duplication cannot bring any combining gain in e.g.,PHY layer. But, PDCP duplication would increase a chance to receive aPDCP PDU successfully/early by obtaining the diversity gain. Frequencydiversity can be achieved by PDCP duplication on different carriers.However, it cannot be guaranteed that time diversity is achieved by PDCPduplication in different TBs on the same carrier or in different TBs ondifferent carriers. If duplicated PDCP PDUs are transmitted on differentTBs within a short period of time, for instance, successively, timediversity gain could be hardly achieved because the channel conditionmay not change in a short period of time. To benefit from time diversityon the same carrier or on different carriers, the duplicated PDCP PDUsneed to be transmitted with a timing difference. Therefore, the presentinvention proposes a way to at least handle the timing differencebetween the duplicated PDCP PDUs transmission.

FIG. 7 illustrates an example of a PDCP duplication according to thepresent invention.

In the present invention, for a PDCP entity configured with PDCPduplication function, the PDCP entity duplicates a PDCP PDU and submitsthe duplicated PDCP PDUs to lower layer(s) with a timing difference. Indetail, the PDCP submits one of the duplicated PDCP PDUs to a lowerlayer and submits another duplicated PDCP PDU after a certain period oftime is passed. In the present invention, duplication at PDCP consistsin sending the same PDCP PDU multiple times. In the present invention,for the convenience of description, the original PDCP PDU and thecorresponding duplicate(s) are all referred to as duplicated PDCP PDUs.

A network (e.g. gNB) configures a PDCP entity to perform PDCPduplication for a PDCP PDU (S701). For example, a network can transmit,to a UE, PDCP configuration information for indicating that a PDCPentity associated with a radio bearer is to perform the PDCPduplication. For the PDCP duplication, a PDCP entity is mapped tomultiple RLC entities or one RLC entity.

In the present invention, for PDCP duplication, the network configures aDuplicationProhibitTimer. In the present invention, theDuplicationProhibitTimer may be running per duplicated PDCP PDU. Forexample, the PDCP entity may start and run a DuplicationProhibitTimerfor a duplicated PDCP PDU of one PDCP PDU until it expires, and maystart and run a DuplicationProhibitTimer for a duplicated PDCP PDU ofanother PDCP PDU. If multiple duplicated PDCP PDUs belonging todifferent PDCP PDUs are submitted to a lower layer, there may bemultiple DuplicationProhibitTimers running at the PDCP entity. The timervalue for the DuplicationProhibitTimer is in unit of time period, or thenumber of PDCP PDUs other than the PDCP PDU making theDuplicationProhibitTimer started. For example, ifDuplicationProhibitTimer is set to 0 ms, the PDCP starts theDuplicationProhibitTimer but DuplicationProhibitTimer expiresimmediately. For another example, if DuplicationProhibitTimer is set to5 PDCP PDUs, the PDCP counts the number of PDCP PDUs that are submittedto a lower layer (e.g. RLC, MAC, and/or PHY) after the PDCP submits aPDCP PDU having started DuplicationProhibitTimer to the lower layer.

When the PDCP receives a PDCP SDU, the PDCP generates a PDCP PDU for thePDCP SDU and duplicates the generated PDCP PDU by a certain number. Thecertain number of PDCP duplication may be configured by the network(e.g. gNB). Namely the network may configure how many PDCP PDUduplicates the PDCP entity is to generate per PDCP PDU. For example, ifthe certain number is two, the PDCP may duplicate the PDCP PDU togenerate two identical PDCP PDUs: one is the original PDCP PDU and theother one is the corresponding duplicate.

If the PDCP entity generates the duplicated PDCP PDUs, the PDCP entitysubmits a duplicated PDCP PDU among the certain number of duplicatedPDCP PDUs to a lower layer (S703). The PDCP entity stores the remainingduplicated PDCP PDUs in PDCP but doesn't submit it to lower layer. ThePDCP entity may generate the certain number of duplicated PDCP PDUs atonce, and submit them one by one after DuplicationProhibitTimer for theduplicated PDCP PDU previously submitted expires and when it is needed,for example, when there is a grant for (MAC PDU) transmission (i.e. whenMAC requests to submit data). Or the PDCP entity may generate oneduplicate by one when it is needed.

When the PDCP entity submits the duplicated PDCP PDU among the certainnumber of duplicated PDCP PDUs to the lower layer, the PDCP entitystarts a DuplicationProhibitTimer for the duplicated PDCP PDU. The PDCPentity doesn't start the DuplicationProhibitTimer for the duplicatedPDCP PDU if the duplicated PDCP PDU is the last duplicated PDCP PDU thatis submitted to the lower layer. For example, if the certain number istwo, the PDCP entity starts a DuplicationProhibitTimer for theduplicated PDCP PDU when submitting the PDCP PDU to the lower layer forthe first time, and does not start the DuplicationProhibitTimer whensubmitting the identical PDCP PDU to the lower layer for the secondtime.

If DuplicationProhibitTimer expires, the PDCP entity submits aduplicated PDCP PDUs among the remaining duplicated PDCP PDUs stored inPDCP to the lower layer (S705). In other words, once a duplicated PDCPPDU (duplicated PDCP 1) of a PDCP PDU is submitted to a lower layer,another duplicated PDCP PDU (duplicated PDCP 2) of the PDCP PDU is notsubmitted to the lower layer while DuplicationProhibitTimer started whenthe duplicated PDCP 1 was submitted to the lower layer is running. Theduplicated PDCP PDU 2 may be submitted to the lower layer when it isneeded after the DuplicationProhibitTimer started when the duplicatedPDCP 1 was submitted to the lower layer expires.

In the present invention, the PDCP submits one of the duplicated PDCPPDUs to a lower layer and submits another duplicated PDCP PDU after acertain period of time is passed. Accordingly, the present invention canensure that the duplicated PDCP PDUs are loaded into transport blockstransmitted at different time instances, whereby time diversity can beachieved. For example, original PDCP PDU is carried by one MAC PDUtransmitted on one time slot, and the corresponding duplicate is carriedby another MAC PDU transmitted on another time slot.

FIG. 8 is a block diagram illustrating elements of a transmitting device100 and a receiving device 200 for implementing the present invention.

The transmitting device 100 and the receiving device 200 respectivelyinclude Radio Frequency (RF) units 13 and 23 capable of transmitting andreceiving radio signals carrying information, data, signals, and/ormessages, memories 12 and 22 for storing information related tocommunication in a wireless communication system, and processors 11 and21 operationally connected to elements such as the RF units 13 and 23and the memories 12 and 22 to control the elements and configured tocontrol the memories 12 and 22 and/or the RF units 13 and 23 so that acorresponding device may perform at least one of the above-describedembodiments of the present invention.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 generally control the overall operation ofvarious modules in the transmitting device and the receiving device.Especially, the processors 11 and 21 may perform various controlfunctions to implement the present invention. The processors 11 and 21may be referred to as controllers, microcontrollers, microprocessors, ormicrocomputers. The processors 11 and 21 may be implemented by hardware,firmware, software, or a combination thereof. In a hardwareconfiguration, application specific integrated circuits (ASICs), digitalsignal processors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), or field programmable gate arrays(FPGAs) may be included in the processors 11 and 21. Meanwhile, if thepresent invention is implemented using firmware or software, thefirmware or software may be configured to include modules, procedures,functions, etc. performing the functions or operations of the presentinvention. Firmware or software configured to perform the presentinvention may be included in the processors 11 and 21 or stored in thememories 12 and 22 so as to be driven by the processors 11 and 21.

The processor 11 of the transmitting device 100 performs predeterminedcoding and modulation for a signal and/or data scheduled to betransmitted to the outside by the processor 11 or a scheduler connectedwith the processor 11, and then transfers the coded and modulated datato the RF unit 13. For example, the processor 11 converts a data streamto be transmitted into K layers through demultiplexing, channel coding,scrambling, and modulation. The coded data stream is also referred to asa codeword and is equivalent to a transport block which is a data blockprovided by a MAC layer. One transport block (TB) is coded into onecodeword and each codeword is transmitted to the receiving device in theform of one or more layers. For frequency up-conversion, the RF unit 13may include an oscillator. The RF unit 13 may include N_(t) (where N_(t)is a positive integer) transmit antennas.

A signal processing process of the receiving device 200 is the reverseof the signal processing process of the transmitting device 100. Undercontrol of the processor 21, the RF unit 23 of the receiving device 200receives radio signals transmitted by the transmitting device 100. TheRF unit 23 may include Nr (where Nr is a positive integer) receiveantennas and frequency down-converts each signal received throughreceive antennas into a baseband signal. The processor 21 decodes anddemodulates the radio signals received through the receive antennas andrestores data that the transmitting device 100 intended to transmit.

The RF units 13 and 23 include one or more antennas. An antenna performsa function for transmitting signals processed by the RF units 13 and 23to the exterior or receiving radio signals from the exterior to transferthe radio signals to the RF units 13 and 23. The antenna may also becalled an antenna port. Each antenna may correspond to one physicalantenna or may be configured by a combination of more than one physicalantenna element. The signal transmitted from each antenna cannot befurther deconstructed by the receiving device 200. An RS transmittedthrough a corresponding antenna defines an antenna from the view pointof the receiving device 200 and enables the receiving device 200 toderive channel estimation for the antenna, irrespective of whether thechannel represents a single radio channel from one physical antenna or acomposite channel from a plurality of physical antenna elementsincluding the antenna. That is, an antenna is defined such that achannel carrying a symbol of the antenna can be obtained from a channelcarrying another symbol of the same antenna. An RF unit supporting aMIMO function of transmitting and receiving data using a plurality ofantennas may be connected to two or more antennas. The RF units 13 and23 may be referred to as transceivers.

In the embodiments of the present invention, a UE operates as thetransmitting device 100 in UL and as the receiving device 200 in DL. Inthe embodiments of the present invention, a gNB operates as thereceiving device 200 in UL and as the transmitting device 100 in DL.Hereinafter, a processor, an RF unit, and a memory included in the UEwill be referred to as a UE processor, a UE RF unit, and a UE memory,respectively, and a processor, an RF unit, and a memory included in thegNB will be referred to as a gNB processor, a gNB RF unit, and a gNBmemory, respectively.

The UE processor can be configured to operate according to the presentinvention, or control the UE RF unit to receive or transmit signalsaccording to the present invention. The gNB processor can be configuredto operate according to the present invention, or control the gNB RFunit to receive or transmit signals according to the present invention.

The processor 11 can generate a PDCP PDU at a PDCP entity of theprocessor 11. If the PDCP entity of the processor 11 is configured withPDCP duplication function, the processor 11 duplicate the PDCP PDU atthe PDCP entity. The processor 11 submits the duplicated PDCP PDU(either original or corresponding duplicate) at the PDCP entity to alower layer and starts a prohibit timer for the duplicated PDCP(duplicate PDCP PDU 1). The processor 11 may submit the same PDCP PDU(duplicated PDCP PDU 2) at the PDCP entity to the lower layer if theprohibit timer expires. The processor 11 may control the transceiver 13of the transmitting device 10 to transmit the duplicated PDCP PDU 1 andthe duplicated PDCP PDU 2. The processor 11 is configured not to submitthe duplicated PDCP PDU 2 from the PDCP entity to the lower layer whilethe prohibit timer is running. The processor 11 may control thetransceiver 13 to transmit at different time instances, respectively.The prohibit timer may be counted in units of time period or in units ofPDCP PDUs submitted to the lower layer. The processor 11 may run theprohibit timer per duplicated PDCP PDU. The processor 11 may runprohibit timer per duplicated PDCP PDU at the PDCP entity. The processor11 may start the prohibit timer for the duplicated PDCP PDU 2 whensubmitting the duplicated PDCP PDU 2 to the lower layer, if theduplicated PDCP PDU 2 is not the last duplication of the PDCP PDU. Theprocessor 11 may not start the prohibit timer for the duplicated PDCPPDU 2 when submitting the duplicated PDCP PDU 2 to the lower layer, ifthe duplicated PDCP PDU 2 is the last duplication of the PDCP PDU. Thetransceiver 13 may receive information on a number of PDCP PDUduplicates that the PDCP entity is to generate per PDCP PDU. Theprocessor 11 may duplicate the PDCP PDU by the number of PDCP PDUduplicates based on the information. The transceiver 13 may receiveconfiguration information for the PDCP entity. The configurationinformation may include information indicating that the PDCP entity isconfigured with the PDCP duplication function. The configurationinformation may include a value for the prohibit timer. Theconfiguration information may include information on a number of PDCPPDU duplicates that the PDCP entity is to generate per PDCP PDU. Theprocessor 11 may duplicate a PDCP PDU at the PDCP entity based on theconfiguration information. The transmitting device 10 may be a userequipment.

As described above, the detailed description of the preferredembodiments of the present invention has been given to enable thoseskilled in the art to implement and practice the invention. Although theinvention has been described with reference to exemplary embodiments,those skilled in the art will appreciate that various modifications andvariations can be made in the present invention without departing fromthe spirit or scope of the invention described in the appended claims.Accordingly, the invention should not be limited to the specificembodiments described herein, but should be accorded the broadest scopeconsistent with the principles and novel features disclosed herein.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention are applicable to a networknode (e.g., BS), a UE, or other devices in a wireless communicationsystem.

The invention claimed is:
 1. A method for transmitting data units by atransmitting device in a wireless communication system, the methodcomprising: submitting, by a packet data convergence protocol (PDCP)entity configured with a PDCP duplication function, a PDCP protocol dataunit (PDU) (duplicated PDCP PDU 1) to a lower layer and starting aprohibit timer for the duplicated PDCP PDU 1; submitting, by the PDCPentity, the same PDCP PDU (duplicated PDCP PDU 2) to the lower layerbased on expiry of the prohibit timer; and transmitting the duplicatedPDCP PDU 1 and the duplicated PDCP PDU 2, wherein the prohibit timerruns per duplicated PDCP PDU.
 2. The method according to claim 1,wherein the PDCP entity does not submit the duplicated PDCP PDU 2 to thelower layer while the prohibit timer is running.
 3. The method accordingto claim 1, wherein the duplicated PDCP PDU 1 and the duplicated PDCPPDU 2 are transmitted at different time instances.
 4. The methodaccording to claim 1, wherein the prohibit timer is counted in units oftime period or in units of PDCP PDUs submitted to the lower layer. 5.The method according to claim 1, wherein the PDCP entity starts theprohibit timer for the duplicated PDCP PDU 2 when submitting theduplicated PDCP PDU 2 to the lower layer, based on the duplicated PDCPPDU 2 not being the last duplication of the PDCP PDU.
 6. The methodaccording to claim 5, wherein the PDCP entity is configured with anumber of PDCP PDU duplicates, that the PDCP entity is to generate perPDCP PDU, by a network.
 7. The method according to claim 1, wherein thePDCP entity is configured with the PDCP duplication function by anetwork, and wherein the PDCP entity is configured with the prohibittimer by the network.
 8. The method according to claim 1, wherein thetransmitting device is a user equipment.
 9. A transmitting deviceconfigured to transmit data units in a wireless communication system,the transmitting device comprising: a transceiver, and a processorconfigured to control the transceiver, the processor configured to:submit, by a packet data convergence protocol (PDCP) entity configuredwith a PDCP duplication function, a PDCP protocol data unit (PDU)(duplicated PDCP PDU 1) to a lower layer and start a prohibit timer forthe duplicated PDCP PDU 1; submit, by the PDCP entity, the same PDCP PDU(duplicated PDCP PDU 2) to the lower layer based on expiry of theprohibit timer; and control the transceiver to transmit the duplicatedPDCP PDU 1 and the duplicated PDCP PDU 2, wherein the prohibit timerruns per duplicated PDCP PDU.
 10. The transmitting device according toclaim 9, wherein the processor is configured not to submit theduplicated PDCP PDU 2 from the PDCP entity to the lower layer while theprohibit timer is running.
 11. The transmitting device according toclaim 9, wherein the duplicated PDCP PDU 1 and the duplicated PDCP PDU 2are transmitted at different time instances.
 12. The transmitting deviceaccording to claim 9, wherein the prohibit timer is counted in units oftime period or in units of PDCP PDUs submitted to the lower layer. 13.The transmitting device according to claim 9, wherein the processor isconfigured to start the prohibit timer for the duplicated PDCP PDU 2when submitting the duplicated PDCP PDU 2 to the lower layer, based onthe duplicated PDCP PDU 2 not being the last duplication of the PDCPPDU.
 14. The transmitting device according to claim 13, wherein thetransceiver receives information regarding a number of PDCP PDUduplicates that the PDCP entity is to generate per PDCP PDU.
 15. Thetransmitting device according to claim 9, wherein the transceiverreceives configuration information for the PDCP entity, wherein theconfiguration information includes (i) information indicating that thePDCP entity is configured with the PDCP duplication function, and iii) avalue for the prohibit timer.
 16. The transmitting device according toclaim 9, wherein the transmitting device is a user equipment.